Apparatus for rectifying high-tension alternating currents



W. A. SCHMIDT. v APPARATUS FOR RECTIFYING HIGH TENS'iON ALTERNATING CURRENTS.

APPLICATION man man. 1916. RENEWED AUG. 23. 1920. 1 58,992, Patented Nov; 16, 1920.

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IIIIIIIIIIIIIIII W. A. SCHMlDT.

APPARATUS FOR RE CTIFYING HIGH TENSION ALTERNATING,CURRENTS. APPLICATION FILED JuuE22 191s. RENEWED AUG-23,1920.

Patented Nov. 16, 1920.

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xum'rro stares PATENT OFFICE.

WALTER A. SCHMIDT, OF LOS ANGELES, CALIFORNIA, ASSIGNOB TO INTERNATIONAL PRECIPITATION COMPANY, 01 LOS ANGELES, CALIFORNIA, A CORPORATION 01' CALIFORNIA.

APPARATUS FOR BECTII'YING HIGH-TENSION ALTERNATING CURRENTS.

Specification of Letters Patent.

Patented Nov. 16, 1920.

Application filed June 22, 1818, Serial No. 105,212. Renewed August 28, 1920. Serial No. 105,482.

T 0 all whom it may concern..-

Be it known that I, \VALTER A. SCHMIDT, a citizen of the United States, residing at Los Angeles. in the county of Los Angeles, State of California, have invented a new and useful Apparatus for Rectifying High- Tension Alternating Currents, of which the following is a specification' This invention relates to means for producin high potential unidirectional current for the purpose of operating apparatus for the electrical treatment of gases. for example, for precipitation of suspended par ticles therefrom.

In electrical precipitatingoperations it has been found that any surges or sudden fluctuations of the current or of the potential difference applied to the load, are objectionable in that they reduce the effective ness of the precipitating action. An important object of the present invention is to eliminate or minimize such sudden fluctuations and to produce from an alternating current. a unidirectional current of smooth wave. form especially adapted for the stated purposes.

In producin such a smooth wave current, it is essential that the current should be continuous .-since any interruption thereof will lead to surging or sudden variations of potential, especially when the circuit presents considerable capacity and inductance, as is generally the case in apparatus of the class referred to. I obtain such continuity by rectifying a poly hase current in such a manner that impu ses will be selected from all the phases successively so as to produce a continuous current. The variations in potential difference, during each of such impulses will depend on the number of phases of the. current, and by usin a polyphase current of a large number 0 phases I may obtain a current of smooth wave form and presenting substantially uniform potential difference at the load. As a further safeguard against sudden fluctuations of current, I prefer to provide rectifying means including electric valve devices which permit current to pass therethrough in only one direction, thereby preventing current from surging back through any part of the apparatus.

Another object of the present invention om alternating current. particularly I is to provide an alternating current rectifier adapted for rectification of alternating currents of extremely high tension The accompanying drawings illustrate embodiments of my invention, and referring thereto:

Figure 1 is a diagrammatic perspective view of one form of the invention.

F g. l is a fragmentary perspective of a portion of the contact members of the rectifier.

Fig. 2 is a similar view showing the application of the invention to a three phase clrcult.

Fig. 3 is a vertical section of another form of the invention.

Fig. 4 is a section on line 4- 1, Fig. 3.

The invention is shown in Figs. 1 and 1 as applied in connection with an alternating current generator, the rectifying devices belng directly connected to the shaft 1 of said generator. In Fig. 1 the rectifier comprises av plurality of circuit controlling members formed, for example, as insulating disks 2 mounted on said shaft and'provided with contacts 3 and 4, there being as many of these disks as there are phases in the current to be rectified. For each disk four stationary contacts 5, 6, 7 and 8 are provided, the contacts 5 and 7 being, for example, opposite one another, and said contacts 5 and 7 of the respective disks being connected by wires 9 and 10 to opposite sides of the secondar windings 11 of stepup transformers. he primary windings 12 of said transformers are connected to the coils or windings 13 of the polyphase alternating current generator 14 mounted on and operated by shaft 1 aforesaid. Contact 6 for each of the disks is grounded at 15' and the opposing contacts 8 for the respective disks are connected by wires 15 to electric valve devices 16 from which wires 17 lead to a line Wire 18 connected to the high tension side of the precipitator, treater, or other load device indicated at 19, the low tension side of said device being grounded as at 20.

The electric valve device 16 may be any high tension valve device and may, for example, consist of a pointed conductor 22 and a plate conductor 23, conductor 22 being surrounded by a tube 24 formed,.for example, of insulating material and connected to a supply tube 25 through which air or gas un er pressure is forced, for example, from a pump 26, in such manner as to produce a current of air extending around the conductor 22 and in the direction of the discharge between the conductors 22 and 23. In place of this valve device any other electric valve device may be used, such as devices of the mercury vapor type, or of the incandescent electrode type.

I prefer to employ, for the contact members of the rectifier, devices such as shown in Fig. 1 whereby an actual contact is secured, instead of an air gap connection such as is generally used in high tension rectifiers. For this purpose each of the fixed contacts 5, 6, 7 and 8 is preferably formed,

as a brush having a plurality of flexible con- -tact members 28 secured to a conductor 28 which is connected to the wire 15 or other wire for leading current to or from the contact member, said flexible contact members 28 being adapted to contact with and ride on the contact members 3 and 4 of the rectifier. The brush contact member described is preferably elongated in the direction of the rotation of the rectifier disk so as to maintain connection with the movable contact member 3 or 4 throughout a considerable arc of the contact, it being understood that the length of the stationary and rotary contact members in the direction of rotation is, in any case, such as to provide for bridging over or making connection between pairs of successive contacts such as 5, 6, and 7, 8, with sufficient overlap to enable successive phases of current delivered by the respective pairs of supply wires 9 and 10 to be impressed uponfthe receiving connections 15 and 15', in such manner that the connection to each pair of wires corresponding to any one phase of the supply circuit is maintained until connection with the next successive pair of wires corresponding to the next phase of the polyphase supply current is effected, whereby a continuous current is secured throughout the load device connected to the rectifier.

The load device 19 is indicated diagrammatically and may for example consist of any of the usual types of treaters for precipitating suspended particles from gases, said treater comprising, for example, header \means 30 for delivering the gases to the treater, and header means 31 for conducting the gases from the treater, the grounded ele: trodes 32 of said treater comprising flues connected to the said supply and outlet headers and the high tension electrodes 33 extending between and insulated from the grounded electrodes 32 and being connected to the high tension line 18. An apparatus of this kind, built and operated on a commercial scale presents considerable electrostatic capacity, by reason of the large surfaces of the electrodes exposed, and operates, in fact, as a leaky condenser, so that there is a tendency for current to flow back from this load device throu h the rectifier whenever the impressed di erence in potential is decreasin Any such tendency of the current to ow back through the rectifier is opposed by the action of the valve devices 16 which serve to prevent current from passing except in one direction. Said valve devices also serve to prevent feeding back from any leg of the high tension transformer o erating momentarily at higher potential ifier" ence, to another leg of the transformer o rating momentarily at lower potential di erence, inasmuch as any such feeding back action through the connections 9 and 10 would cause a current in a direction opposed by the electric valve connected to the transformer leg which is operating momentarily at lower potential difference. By thus preventing sudden backflow or reversals ofcurrent, either from the load or from one transformer'to another, we prevent the surges or abnormal currents which would be produced by such sudden changes of current, and thereby insure the maintenance of a current of smooth wave form.

In this connection it should be noted that in the actual construction of the apparatus, it is not practicable to break the connection to any transformer leg at the very instant that the next leg comes into connection, but

there must be some overlap of the connections. The contact shoes 3 and 4 on the di 5- ferent disks 2 and the stationary contacts 5, 6, 7 and 8 are so related and disposed as to cause a sufficient period of overlap of the phase connections. During this period of overlap, the potential difference is decreasing in the leg to which connection is about to be broken, and is increasing in the leg to which connection has just been made. At some time in this period of overlap there will be a differential effect between the two legsthus simultaneously connected in circuit, which would result in sudden generation of local currents and consequent surging in the line, if this were not prevented by the action of the valves as above set forth. The differences of voltage produced in different transformer legs in this manner will, in any case be small compared to the total voltage of the transformer secondar windin s, and the valve device above described will proportioned and adjusted in such manner as to properly check the reverse current even with such relatively small differences of potential. ment of the valve devices, said devices will not, in general, be adapted to check the full line voltage of the high tension circuit, and the inclusion of mechanical rectifier devices in the connections to the respective valve devices is therefore of advantage in discon- With such construction and adjust- .tion as the number 0 mum necting each valve device at times when excessive potential difference would be duced therein in a direction which shoul checked or prevented b the valve.

Fig. 2 shows an app ication of the invention m connection with a three phase circuit, the construction being similar to that above described in connection with Fi 1, this figure showing also the use of the e onted comb-like brushes, such as shown in ig. 1. The shaft 1 of the mechanical rectifier is in this case shown as driven by a s chronous motor 14', connected to the t ree phase supply circuit indicated at 34, 35, 36, which is connected to the primary windings 12 of the step-up transformer.

By the construction above described I provide for production of a unidirectional current having a smooth wave form, thecircuit connections to the load being maintained continuously so that there is no sudden breaking of circuit, with resultin surges or sudden chan in the current. 11 any electric circuit 0 this character presenting considerable inductance and capacity there is a tendenc to sudden oscillations or surges on any su den make or break of a circuit, and by providing for continuity of the circuit connection, obviate any liabillty of such sudden variations in the current due to make or break of the circuit connection. Furthermore, the electric valves check any tendency to surging of current in the circuit connections, thereby producln a current which is unidirectional and whic has a substantially smooth wave form, the undulations or variations of amplitude or of potential difference in any wave bein smaller 1n ropor- .phases use is increased, so that, by suitably increasin the number ofphases, any desired uniformity in the potential difference in the circuit may be obtained.

In case extremely high potentials are to be rectified, the construction shown in Figs. 3 and 4 is referably used, the same comprising recti er disks 2 mounted on a shaft 1 which is journaled in the bearings 40-and 41 and is operated by a synchronous motor or other device 14 operated in synchronism with the alternating current, said disks 2 carrying contact segments 3 and 4 as above described, making connection with stationary contacts 5,- 6, 7 and 8 mounted around each disk. Contacts 6 are grounded as indicated at 15, and contacts 5, 7 and 8 are mounted on insulating sleeves 44, 45, 46, extending throu h the walls of a casin or cylinder 47. Said casing or cylinder is closed at each end, for example by means of end plates 48 and 49, and is adapted to contain a gas under pressure, for example carbon d1- oxid gas furnished thereto through a valvedv inlet 50. The bearing 41 for shaft 1 is provided with stuflin'g box 51 to enable the presv the transformer 11' being sure within the chamber or casing to be maintained. The contacts 5 and -7 are connected by the wires 9 and 10 to secondary windings 11 of the lyphase transformer 11 Each contact 8 is connected to an electric valve device 16 from which a wire 18 leads to the treater 19 as above describer In order to further insulate the connections, t is preferred to immerse the whole device, mcluding the casing 47 in a body of insulating liquid such as oil, indicated at 54 and contained within a casing or tank 55, also immersed in this same body of oil, so that all the electric connections are oil-insulated. The dielectric strength of the gas within the casing 47 increases with the pressure, so that by maintaining the gas within said casing at a suitably hlgh pressure any desired degree of insulatlon may be secured therein, and alternatingcurrent'voltage up to or exceedin five hundred thousand volts ma be rectified, using rectifier disks of much less than the ordinary dimensions of the open air rectifiers now in general use for potential differences of about 50,000 volts. In this connection it is desirable to provide for actual contact of the rectifier contacts or segments 3 and 4 with the stationary contacts 5, 6, etc., in order to prevent, as far as possible, arcing or burning of the contacts under the extremely high otential difierences above referred to, and or this purpose brush contacts such as shown in Fig. 1 may be used to advantage. With such actual contact, however, the use of the electric valves 16 becomes of especial advantage, since the sudden breaking of connections in any leg of the transformer resulting from the openin of the actual contact would otherwise res t in induced currents presenting surges or abnormal currents in the circuit as above described.

- The fact that the contacts are separated in an atmosphere of highly compressed s also tends to produce more sudden breaking of the circuit, with resulting sur es, and the use of the electric valves is t erefore of especial advantage in connection with a rectifier of this type. By immersing the rectifier bodily in the oil in the transformer case, the important advanta e' is obtained that all the connections are either in highly insulating oil or in highly insulating compressed gas, the only connection that leads to the outside being the wires ,15 leading to the electric valves. In some cases the electric valves may be omitted and a single high tension connection, extending up through the oil and leadin to the loa will then suflice.

What I claim is:

1. In combination with a load device and a high-tension polyphase circuit, means for successively connecting the diflerent phases of said circuit to the load, said means being so constructed and arrangedthat each phase is connected to the load before its voltage becomes zero and before a previously connected phase is disconnected, and means for preventing cross-currents between thephases.

2. In combination with a load device and a high-tension polyphase circuit, means operated in synchronism with said circuit for successively connecting the separate phases to the load, said means being constructed and arranged to continue the connection be-. tween one phase and the load until connection between another phase and the load is made, and an asymmetric conductor element in series with each phase for preventing current flow in reverse direction.

3. A high tension alternating current rectifier comprising stationary contacts connected respectively to alternating current supply wires and to load connections, a rotary member provided with conductors adapted to cooperate with the stationary contacts to rectify the alternating current, a casing inclosing said contacts and adapted to contain gas under pressure, electric valve means included in the load connections of said rectifier. and a tank surrounding said casing and adapted to contain an insulating liquid for immersing said circuit connections.

4. Means for producing unidirectional high tension current comprising a high tension step up transformer, a mechanical rectifier having connections to said transformer and load connections, and having a shaft provided with conductor means for periodically making and breaking connection be tween the transformer and load connections to apply rectified current to the load connections, means connected to said shaft to operate the said conductors in synchronism with said current, a casing surrounding said mechanical rectifier and adapted to contain gas under pressure, and a receptacle inclosing said casing said transformer and the connections thereof and adapted to contain oil for immersing said transformer and connections.

5. The combination of a. mechanical rectifier having stationary contacts provided 'with polyphase alternating current supply connections, stationary contacts provided with load connections, a rotary means comprising conductors for cooperation with said stationary contacts and means for operating said rotary means in synchronism with the alternating supply current for periodically and successively connecting the different phases of the polyphase alternating circuit to said load connections, said rotary means including parts adapted to supply an uninterrupted unidirectonal current thereto, and asymmetric conductor elements cooperating with certain of said stationary contacts whereby unidirectional current flow to said rotary means is determined.

6. A mechanical rectifier comprising stationary contacts having connections to respective phases of a polyphase alternating circuit and stationary contacts having load connections, means for successively interconnecting said contacts so as to deliver an uninterrupted unidirectional current supplied in part from each phase of the polyphase circuit, and asymmetric conductor parts interconnecting said load connections and said supply phases, whereby flow of cross currents between said phases is prevented.

In testimon whereof I have hereunto set my hand, at 05 Angeles, California, this 8th day of June, 1916.

WALTER A. SCHMIDT. 

